Influence of Crystallization Condition on Structure of P(VDF-CTFE) Copolymers
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0889-W07-03.1
Influence of Crystallization Condition on Structure of P(VDF-CTFE) Copolymers Xin Yang, Zhimin Li, LeVar Odum and Z.-Y. Cheng Materials Research and Education Center, Auburn University, Auburn, Alabama 36849 ABSTRACT
The influence of the crystallization condition – temperature and time – on the structure of poly (vinylidene fluoride chlorotrifluoroethylene), P(VDF-CTFE), was studied using DSC and XRD. The DSC results of all studied polymers show three peaks. One peak, which is associated with crystallization temperature, represents the appearance of unstable phase in the polymers. Both XRD and DSC data indicate the coexistence of different phases in the polymers, which may be the reason for the high electrostrictive performance obtained in the polymers. INTRODUCTION PVDF based polymers have been extensively investigated since its discovery in 1960’s. However, the electromechanical (E-M) performance, such as piezoelectric constant and E-M coupling factor, of piezoelectric PVDF homopolymer and PVDF-based copolymers is much lower than that of the piezo-ceramics. In order to improve its E-M performance, different approaches have been investigated in recent years. For example, a high electrostrictive strain response (~5 %) with an E-M coupling factor of (~30 %) has been obtained in highenergy-electron-irradiated P(VDF-TrFE) copolymer [1,2]; high electrostrictive response is also observed in PVDF-based terpolymers, e.g. P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) [3,4]. Regarding the mechanism of electrostrictive polymers, it is found that the electrostrictive response obtained in high-energy-electron irradiated P(VDF-TrFE) copolymers originates from the electric field induced the conformation/structure change [5]. However, a systemic study on P(VDF-TrFE-CTFE) terpolymers indicates that besides the electric field induced conformation/structure change and the Maxwell stress effect there are other unknown mechanisms responsible for the high E-M performance observed in the polymers [6,7]. In a systemic study on the re-crystallization in the high-energy-electron-irradiated P(VDF-TrFE) copolymers, we found that the partially ordered region, such as the interfacial layer in semicrystalline polymers, plays an important role in the high E-M performance observed in PVDF-based electroactive polymers [8]. The concept of partially ordered regions was also used to explain the stress dependence of strain response observed in dielectric elastomers [9]. In our recently study, we find that P(VDF-CTFE) copolymers exhibit a high electrostrictive response, a strain response of 5 % with an E-M coupling factor of 40 % [10]. To understand the high E-M response observed in P(VDF-CTFE) copolymers, the structure and its transformation for P(VDF-CTFE) samples crystallized at different conditions were studied using DSC and XRD. The results are reported in this paper. The coexistence of different phases was founded in all the P(VDF-CTFE) copolymers studied here.
0889-W07-03.2
EXPERIMENTAL
RESULTS AND DISCUSSIONS Differential Scanning Cal
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